Blossom End Rot on Tomatoes
Saturday, May 17, 2003
Blossom end rot is a blackening of the end of the tomato (side opposite of where attached to vine). This blackening or rotting may either be just a small black spot, or it may result in up to one half of the tomato blackened. Blossom end rot does not affect the quality of the unaffected part of the tomato, but it reduces tomato yield, and is not very attractive.
Blossom end rot is a physiological disease that results from the lack of calcium available to the tomato as it develops. If the tomato is rapidly growing, and if calcium is in short supply, the tomato uses the calcium for vegetative development, and not for fruit development.
Weather conditions in the Heartland that promote calcium end rot are lots of rain in the early spring when tomatoes are rapidly developing. Above normal rain leaches calcium out of the upper surface of soils, therefore making it unavailable for tomato root uptake.
You can correct the problem by applying more calcium, in the form of lime or gypsum, to your garden soil. It takes a while for this calcium source to become available to plants. You can also spray the tomatoes on the vines with a weak calcium chloride solution. Spray the developing tomatoes every week until harvest. One source of calcium chloride is a product called Yield Booster formulated by fertilome.